Acoustical diaphragm



Feb. 5, 1935. A. E. N. LAWRANCE 1,990,409

ACOUSTICAL DIAPHRAGM Filed Feb. 8, 1933 000006 0 6 0 0 0 0060000000 v 6 o o [0 O O 00 O 8 o o o 9 F7 5. vwvrance Patented Feb. 5, 1935 1,999,499 ACOUSTICAL DIAPHRAGM Athol Ernest Neville Lawrance, Kenilworth, Johannesburg, Union of South Africa Application February 8, 1933, Serial No. 655,844 In the Union of South Africa Februhry 19, 1932 Claims. (Cl. 181-92) The present invention relates to diaphragms for acoustical apparatus such as microphones. loud speakers, phonographs and musical instruments.

l The object of theinvention is to improve the sensitiveness of .the diaphragm to sound vibrations covering a wide range of frequency and thereby to enhance the clarity of the recorded or reproduced sound and ensure that it represents the original sound truly and without distortion, more particularly in the case of speech or music.

According to the present invention, successive sectors of the diaphragm are progressively stiffened so as to form a continuously progressive series occupying the circumferential extent of the diaphragm.

The diaphragm is thus made selectively responsive to a series of sound wave lengths which themselves constitute a continuous and systematic progression.

The invention is illustrated in the accompanying drawing in which,

Figs. I to V are face views of different forms of-diaphragms.

Figs. VI and VII are cross sections of Fig. IV taken on VI-VI and VII-VII respectively.

Fig. VIII is a cross section taken on line VIII VIII of Fig. I, I

8. IX is a cross section taken on line IX-IX of Fig. 11,

Fig. X is a cross section taken on line X-X of Fig. III.

Various ways of making a diaphragm with sectors differing in stiffness are shown. The diaphragm may for instance be formed with corrugations which are different in different areas of the diaphragm. Fig. 1 shows a diaphragm 2 formed of a single sheet of material in which are formed a number of radialcorrugations 3.

These are spaced differently in diflerent areas of the diaphragm, so that a sector such as that defined by the radii 5, 6, is stiffer than the sector defined by 8, '7 in which there are fewer corrugations but less stiff than the sector bounded by 4, 5, in which there are more corrugations. Preferably the stiffness is made to vary progressively around the diaphragm by progressively varying the pitch of the corrugations. Fig. II shows another form of corrugateddiago phragm in which the corrugations are equally pitched and the progressive variations of stiffness is effected by progressively varying the length of the corrugations.

Fig. III'shows another corrugated diaphragm u in which the corrugations 3 are circumferential and of varying angular extent.

In the diaphragm shown in Fig. IV, stiffening of the sheet material forming the diaphragm is effected by'e numerous dots 8 thereon.

By way of example this figure also shows a more definite stepping of the stiffness variation as compared with the substantially progressive variation indicated in the preceding figures. The area of the diaphragm is divided by imaginary diameters 9, 9, 10, 10 into the four sectors 11, 12, 13, 14. The dots 8 in all sectors being of the same diameter and depth, they are most in number and most closely spaced in sector 11 which is accordingly the stiifest sector. Sectors 12, 13, 14 in turn are provided with successively fewer and more widely spaced dots so that said sectors are successively less stiff.

Another way in which the stifiness may be varied is by differentiating the thickness of the diaphragm in diiferent areas. Figsl V, VI and VII show a diaphragm comprising a circumferentially complete single sheet 15. On this is cemented a second sheet 16 forming a sector of 2'70 degrees, then a third sheet 17 forming a sector of corrugations which are of uniform width and height and vary in aggregate length in equal sectors of the diaphragm so as to form a continuously progressive series embracing the whole circumferential extent of the diaphragm.

3. An acoustical diaphragm successive sectors of which are made of varying stiffness by means of radial corrugations of uniform width and height, the pitch of said corrugations varying progressively so as to form a continuously progressive series embracing the whole circumferential extent of the diaphragm.

4. An acoustical diaphragm successive sectors of which are made of varying stiffness by means of radial corrugations of uniform width and height, said corrugations progressively varying in length so as to form a continuously progressive series embracing the whole circumferential extent of the diaphragm.

5. An acoustical diaphragm successive sectors of which are made of varying stiffness by means of circumferential corrugations of uniform width and height said corrugations diii'ering from one another in angular extent so as to form a continuously progressive series embracing the whole circumferential extent of the diaphragm.

ATHOL ERNEST NEVILLE LAWRANCE. 

